Several alternative renewable energies have been discovered to meet the energy saving requirements. Recently, Grätzel and O'Regan have disclosed a dye-sensitized solar cell (DSSC) for efficiently utilizing solar energy, thereby largely attracting industry attention. A general DSSC structure includes four parts: an anode/cathode to provide a flow path of current, a semiconductor TiO2 to accept electrons, a dye layer, and an electrolyte to transport electron holes. Materials of the DSSC parts and interface structures between the DSSC parts may influence a device efficiency of the DSSC; however, a dye in the dye layer is most critical in the DSSC. As such, a dye molecule may reach the best efficiency of the DSSC is one of the topics in this field.
A dye with a complex with a ruthenium center (e.g. N3 dye, (cis-dithiocyanato-bis(4,4′-dicarboxy-2,2′-bipyridine) ruthenium) has the highest conversion efficiency among the conventional dyes. However, ruthenium costs expensive due to its low reserves. A novel dye is called-for to replace the best ruthenium dye N3. For example, organic dyes are candidates due to their high absorption coefficient, tunable structure, and easily obtainable properties; especially their high absorption coefficient thereof (the most critical property of photo sensitive dyes). As such, organic dyes have excellent development potential.
Although the organic dyes have many advantages as described above, there is no organic dye really utilized in a DSSC due to their low stability, low durability, and low conversion efficiency. Therefore, designing a novel organic dye having high absorption coefficient and high conversion efficiency is a topic in the field of optoelectronic conversion devices.